Cursor flicker on subform

[Wiz]

I have a form in an Access ADP app that exhibits weird behavior on a
few PCs in the office.

The app was originally coded in Access 2000 and win2k, and now runs
under Access 2003 and WinXP. It's a single form with a tab control
coded with 6 tabs and mostly bound sub forms beyond the first tab. The
last tab contains a bound tablular subform, linked to a form on
another tab..

When the user navigates to the last and creates a new record, the
cursor starts flickering between the arrow and hourglass. The first
column on the form is a drop down list that's bound to a small table
for lookup, and the second column is bound to a date column in the
table. The flickering usually starts when the user starts typing in
the date field, and throws a validation error before the user is able
to finish typing a date. This app doesn't have a heck of a lot of code
behind it, and it doesn't appear to be doing anything with events at
all.

I've rebuilt the subform from scratch with the same result. As I said
at the start, some PCs in the office don't exhibit this behavior, some
do.

Any ideas?